Tierney's interests in genetics and cell wall dynamics is aimed at understanding regulation and function of structural components of plants' cell wall, both in determining cell form and function during plant development and in providing a defense strategy for plants in response to physical damage and pathogen infection. One of her research areas is study of a family of proline-rich cell wall proteins in Arabidopsis (AtPRPs) whose function is involved in tailoring the structure of the plant cell wall in root hairs and stomata. She used gene fusions in transgenic plants to show that AtPRPs is limited to these cell types and is linked to factors that control cell growth. Among Tierney's publications are: "Expression of AtPRP3, a proline-rich structural cell wall protein from Arabidopsis thaliana, is regulated by cell-type specific developmental pathways involved in root hair formation" (Plant Physiology, 2000, co-authors); and, "Arabidopsis PRPs Derive From Two Distinct Subsets of Proline-rich Cell Wall Protein Genes Encoding Multiple-domain Proteins" (Plant Physiology, 1999, co-authors).